1. Field of the Present Invention
The present invention generally relates to the field of heat dissipation in data processing systems and more particularly to an assembly for maintaining a heat sink in contact with an electronic device such as an integrated circuit module.
2. History of Related Art
In many data processing systems (computers) having one or more socketed processors, heat is transferred from the processor to a directly attached heat sink to cool the device. A spring is typically used to press the flat surface of the heat sink base against the flat top surface of the processor to facilitate thermal dissipation away from the processor and to hold the assembly in place. As size and weight of heat sinks continue to increase with increases in processor speed and power, maintaining adequate contact force between the chip and the heat sink has become a design challenge. With large heat sinks already in the 300 to 800 gram range, it has become increasingly difficult to satisfy minimum system fragility requirements while also maintaining the contact force below the chip manufacturer specified limits. Improved heat sink to chip retention is needed to avoid a dramatic increase in fragility-related failures such as clip failures, heat sinks falling off processors, and the like.
The problems identified above are in large: part addressed by a heat sink retention assembly for maintaining a heat sink in contact with an electronic component such as microprocessor or other integrated circuit module. The assembly includes a spring, a spring retainer, and a spring displacement limiter. The spring retainer maintains the spring in a compressed state in which a contact portion of the spring applies a force to the heat sink. The compressed state is characterized by a predetermined spring displacement and exerted force. The spring displacement limiter prevents spring displacement significantly beyond the. predetermined spring displacement. The displacement limiter may comprise a separate component such as a spacer structure or may be integrated into the configuration of the spring itself. In one spacer structure embodiment, the spacer has a vertical dimension that is determined by the difference between the total spring displacement possible and the predetermined spring displacement required to deliver the predetermined force to the heat sink. When the spacer is placed between a bowed portion of the spring and the heat sink, it contacts both the spring and the heat sink when the spring is in the compressed state thereby preventing additional displacement. Alternatively, the spacer may be sized to leave a small gap between the spacer and the heatsink when the spacer is in contact with the bowed portion of the spring and the spring is in the compressed state. This small gap would permit slight, temporary movement of the heatsink in the event of mechanical shock.